Treating veneers



y 1963 R. HILDEBRAND 3,099,541

TREATING VENEERS Filed March 24, 1961 x9 p 5 25 in a 3 7 9 D M 15 o f; I/ Q I I 0 *7 l 1 w 1 4 7 3/ i I 1 Fig 5 lNl/ENTOP Robe/"f #z'la'ebmnd BY k 7 gram/6Y5 United States Patent 3,099,541 TREATING VENEERS Robert Hildebrand, Nurtinger Str. 68, Oberborhiugen, Wurttemberg, Germany Filed Mar. 24, 1961, Ser. No. 98,203 3 Claims. (Cl. 34-18) This invention relates to the treatment of veneers and, in particular, to the removal of water from veneers freshly peeled from a log.

Veneers freshly peeled from a log contain a considerable amount of moisture in the form of free water. Ordinarily this water is removed by being vaporized through the application of hot air to the surface of the veneer. The drying of the veneer in the open air is seldom used in view of the time required. Inasmuch as the moisture in the freshly peeled veneer is not evenly distributed over the surface of the veneer, a considerable problem exists in drying the veneer to a uniform moisture content throughout, particularly when the drying is done by the use of hot air having a temperature above 100 C. For example, the moisture content on the surface of the veneer can vary as much as from 200% by weight of the veneer in one spot to 60% in an adjacent spot, with no regular distribution of such spots over the surface of the veneer. Therefore, it has been extremely difficult to finally dry the veneer to a uniform moisture content throughout as, for example, to a 6% moisture content within a reasonable time.

The object of this invention is to treat freshly peeled veneer so as to remove the free surface Water therefrom so that the thus prepared veneer can subsequently be quickly and uniformly dried by means of hot air.

In general, these and other objects of the invention are obtained by directing a strong blast of atmospheric air against the surface of a moving sheet of freshly peeled veneer. This air blast blows the free water from the open cells in the surface of the veneer and a wave of the liquid more or less in the form of foam drips or drains from the surface of the advancing sheet of veneer. Thus the surface of the veneer which has passed through the air blast has been freed of most of the water originally contained on the veneer surface, and this water has been removed in the form of liquid by means of atmospheric air at ambient temperature and humidity and without any attempt to vaporize the water in order to dry the veneer surface. The residual water held at the saturation point of the wood fibers is substantially evenly distributed over the surface of the board so that in a subsequent drying of the veneer by hot air, the water content can be quickly reduced to 6% uniformly distributed throughout the veneer.

The means by which the objects of the invention are obtained are described more fully with reference to the accompanying drawings, in which:

FIGURE 1 is a perspective view of a freshly peeled veneer sheet showing the uneven distribution of water on the surface thereof;

FIGURE 2 is a diagrammatic cross-sectional view through the apparatus of this invention used to remove the water from the veneer; and

FIGURE 3 is a perspective view partially shown in section of the air blast nozzle used for removing the water.

As shown in FIGURE 1, a sheet A of freshly peeled veneer up to about 3 mm. in thickness has on its surfaces freshly cut open cells extending as far as mm. into the veneer and which contain free water. The quantity of water is not uniformly distributed over the surface of the board with the result that one area B may contain from 150 to 200% of water with respect to the weight of the veneer while an immediately adjacent area C may 3,09ii,541 Patented July 30, 1963 "ice contain only 60% of water. This irregular distribution of water varies in the length of the sheet of veneer and also varies in accordance with the type of wood. It has been discovered that this exposed free water amounts to the greatest portion of the water which may be removed from the veneer and that only a minor portion of the water is bound in a sheet of veneer of up to about 3 mm. thickness.

As shown in FIGURE 2, a frame 1 supports pairs of rollers 3, 5 and 7 between which a sheet of veneer is passed in the direction of the arrow 9. Ordinarily the veneer is dried by being passed through a tunnel con taining hot air nozzles 11 and 13 mounted in housings or hot air boxes 17 and 19, respectively, which hot air vaporizes the surface moisture to dry the opposite surfaces of the veneer. However, as indicated in FIGURE 1, such drying is not effective to dry the veneer uniformly over the entire surface thereof.

According to this invention, the the sheet of veneer, before reaching the hot air tunnel, passes between air blast boxes 21 and 23, respectively, having nozzles 25 and 27 disposed on opposite sides of the veneer. The air blast nozzles extend entirely across the width of the sheet of veneer, and the side edges of the veneer are supported by post 31 against which the veneer is urged by spring 33. The boxes 21 and 23 are adjustably mounted on bracket 29 so that the wgle of the air blast against the surface of the veneer can be varied according to the type of wood being treated.

As shown in FIGURE 3, each of the boxes is substantially rectangular in shape for receiving compressed air from a blower, and this air is substantially evenly distributed through the baffle openings in the nozzles 25 and 27. The individual openings formed by the baffles have a maximum cross-sectional dimension of from 6 to 10 mm.

In operation, the angle of the air blast nozzles with respect to the horizontal surface of the veneer is set anywhere from 25 to 70, depending upon the type of wood being treated, the velocity of the air blast, and the speed of the sheet of veneer. The air blast issuing though the nozzles can be from about 25 to 40 meters per second, this blast being directed to the nozzle openings in nozzles 25 and 27. As the sheet of veneer is advanced in the direction of the arrow D, the air blast physically blows the free water from the open cells of the wood in the form of a more or less liquid foam. The water flows off the surfaces in the form of liquid and drips or drains to the fioor. Any vaporization of the water is negligible. The sheet of veneer leaving the air blast nozzles has had its moisture content reduced anywhere from 150 to 200% by weight of the veneer down to the saturation point of the wood fibers which is about 40 to 50%, and this residual moisture is uniformly distributed over the surface of the veneer. The sheet of veneer then passes between the heated hot air boxes 17 and 19 wherein the remaining surface moisture is quickly reduced by being vaporized in hot air down to about a 6% moisture content in the veneer. This final reduction is accomplished very rapidly, and the dried veneer coming out of the heat tunnel is substantially uniformly dried throughout and does not have any wet patches which can be equalized only by prolonged storing of the veneer sheet with the hazard of the overdrying and cracking of portions of the veneer.

In a specific example, a sheet of veneer of poplar wood 1 mm. in thickness and having an overall moisture content of per sheet of wood was passed between the air blast nozzles 25 and 27 at the rate of 250 mm. per minute. The air blast nozzles with 6 mm. openings were fixed at an angle of 40 with respect to and 30 mm. away from the surface of the veneer. The air blast was composed of atmospheric air at ambient temperature and humidity and was introduced through the nozzles at the rate of 32 meters per second. The water mechanically freed from the surfaces of the board and drained off the surfaces in the form of a liquid was such as to reduce the moisture content of the veneer to 50%. In the subsequent hot air drying between the hot air boxes 17 and 19, the moisture content Was reduced to 6% using hot air at 160 C.

The advantages of this invention lie in the fact that the major portion of the water is removed mechanically from the freshly peeled veneer by the use of atmospheric air at ambient temperature and humidity and thus avoiding the cost of heating large quantities of air. The removal is rapid with relatively inexpensive equipment, and the time for the final drying With hot air is rapid and with the use of far less quantities of hot air than heretofore needed. In addition to the rapidity and simplicity of the process and apparatus, the finally dried sheet of veneer is substantially uniformly dried throughout and needs no further treatment.

Having now described the means by which the objects of the invention are obtained, I claim:

1. A method of treating fresh peeled veneer having a thickness up to about 3 mm. comprising directing a blast of atmospheric air at an acute angle against the surface of the veneer to blow the free water out of the freshly cut open cells in the veneer as a wave of foam over and from said surface in liquid form to reduce the water content of the veneer from about 120 to not more than about by weight of veneer.

2. A method as in claim 1, further comprising blowing said air onto said surface at an angle of from about 25 to and at a velocity ranging from about 25 to 40 meters per second.

3. A method as in claim 2, further comprising the final step of applying hot air at a temperature of about C. to said surface to dry said veneer to about 6% moisture content.

References Cited in the file of this patent UNITED STATES PATENTS 835,843 Baetz Nov. 13, 1906 1,955,977 Ross Apr. 24, 1934 2,378,703 Hanson June 19, 1945 2,388,226 Hanson Oct. 30, 1945 2,803,446 Flynn Aug. 20, 1957 2,882,611 Debrie Apr. 21, 1959 FOREIGN PATENTS 217,642 Great Britain June 17, 1924 

1. A METHOD OF TREATING FRESH PEELED VENEER HAVING A THICKNESS UP TO ABOUT 3 MM. COMPRISING DIRECTING A BLAST OF ATMOSPHERIC AIR AT AN ACUTE ANGLE AGAINST THE SURFACE OF THE VENEER TO BLOW THE FREE WATER OUT OF THE FRESHLY CUT OPEN CELLS IN THE VENEER AS A WAVE FO FOAM OVER AND FROM SAID SURFACE IN LIQUID FORM TO REDUCE THE WATER CONTENT OF THE VENEER FROM ABOUT 120 TO NOT MORE THAN ABOUT 50% BY WEIGHT OF VENEER. 